chore: unify the labs under one GitHub Pages site

Each web demo builds with its base path under /ai-coding-workflow-labs/,
a single deploy workflow assembles them with a root index, and the
per-directory workflows from the standalone repos are removed.

gstack/astro.config.mjs

@@ -3,7 +3,7 @@ import tailwind from '@astrojs/tailwind';
 import sitemap from '@astrojs/sitemap';
 
 const siteUrl = process.env.SITE_URL ?? 'https://tiennm99.github.io';
-const basePath = process.env.SITE_BASE ?? '/try-gstack';
+const basePath = process.env.SITE_BASE ?? '/ai-coding-workflow-labs/gstack';
 
 export default defineConfig({
   site: siteUrl,